Throughout history, various studies have recognized the fact that there is a relationship between psychological stress and changes in physiological states. One manner in which this relationship has been employed is in the causation of programmed response to psychological stimuli, a technique that has most notably been documented by Pavlov in his experiments with conditioned responses. Essentially the same characteristics have provided some basis for the development of techniques in such diverse fields as applied psychology, advertising and hypnotism. Although the existence of this aspect of the psycho-physiological relationship is well recognized, it is only indirectly involved with the present invention.
The second general type or category of the psycho-physiological relationship, which is of more direct interest to the present invention, involves the recognition and identification of physiological changes, which occur when the psychological changes take place. This approach is used more often in medical and psychological research and diagnosis, and in lie detection.
If the physiological manifestations of a change in psychological state are sufficiently great, it is possible for some subjective evaluations to be made by observation by a trained observer. However, far more accurate evaluation can be made by instrumentation designed to detect and measure relatively small degrees of physiological change. Those physiological changes most usually considered are brain wave patterns, heart activity, skin conductivity and breathing activity.
While the measurement of these activities does provide a far more accurate evaluation of physiological response than direct unaided observation, it introduces several disadvantages. The most functionally serious of these problems is the artificiality of the testing situation caused largely by the previous requirement that sensors be attached to the person who is the subject of the examination. In addition, techniques heretofore used have generally required a controlled environment with resultant restrictions on the normal activity of the subject. These requirements can be expected to induce a psychological “set” in the subject which, in some cases, may be as strong as, or stronger than, the psychological set which is to be evaluated, thereby substantially reducing the validity of the evaluation.
An object of the present invention is to provide a method of removing audio psychological stress indicators by detecting and altering manifestations of physiological changes wherein the traditional restraints are minimized or eliminated to the extent that, in most cases, the subject need not be concerned that he is being examined.
A further object of the invention is to mask the human voice medium such that natural changes in physiological state in response to psychological stress are rendered undetectable.
A further object is to provide an apparatus for providing a real-time variation of those naturally occurring characteristics of the human voice by which physiological changes can be recognized and from which the existence of psychological stress can be determined.